The mutation theory; experiments and observations on the origin of species in the vegetable kingdom . Fig. 127. Casiiarina quadrivalvis. A branch with a hitcraltorsion, a. From the botanical garden in Anisterdani,1897. Silcne nodi flora and other species which occasionallyproduced spiral torsions in my cultures. In J^alcrianaofficinalis (Fig. 122, p. 528), which has already beenmentioned, the proportion of anomabms individuals raised 540 Heritable Spiral Torsions. from seeds gathered from twisted stems was very small,and in Rubia tinctorum, of which I have had severalbeautiful instances of spi
The mutation theory; experiments and observations on the origin of species in the vegetable kingdom . Fig. 127. Casiiarina quadrivalvis. A branch with a hitcraltorsion, a. From the botanical garden in Anisterdani,1897. Silcne nodi flora and other species which occasionallyproduced spiral torsions in my cultures. In J^alcrianaofficinalis (Fig. 122, p. 528), which has already beenmentioned, the proportion of anomabms individuals raised 540 Heritable Spiral Torsions. from seeds gathered from twisted stems was very small,and in Rubia tinctorum, of which I have had severalbeautiful instances of spiral torsions from the fields inHolland, they are never by any means common, although. Fig. 128. Agrostemma Githago. The calyx is open at oneside and fused with the uppermost pair of leaves andtransformed into a spiral. Culture of 1896. they occur nearly every year.^ In Agrostemma GithagoI have often observed torsions in a race which I havecultivated during ten generations since 1888, but always ^ Eenige gevaUcn van Klemdraai by de Meehrap (Riibia tinc-torum). Botan. Jaarb. Gent, 1891, p. 74 and Plate IV. Rare Spiral Torsions. 541 in small numbers. Sometimes these were confined to thevegetative parts, but sometimes the calyx, together withthe upper pair of leaves, was transformed into an openspiral (Fig. 128). In order to determine the intensity of inheritance ofthis anomaly in such cases, I have conducted an experi-ment with Dipsacus laciniatus. This plant was of pecu-liar interest to me because it belonged to a genus whichhas been known for a long time to produce fine spiraltorsions and to which also the Dipsacus sykcstris be-longs, from which I have been able to isol
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